Formation of novel TRIP-ductilized bulk metallic glass composites by manipulating nucleation kinetics via minor alloying

A series of conical bulk metallic glass composites(BMGCs)with compositions of Zr_(47)Cu_(47-x)Al_(5)Ag_(1)Ga_(x)(x=0,1,2,4;at%)were synthesized using the minor alloying method to investigate the effect of Ga addition on the glass-forming ability(GFA),micro structure uniformity and mechanical properties.

Corrosion and irradiation behavior of Fe-based amorphous coating in lead-bismuth eutectic liquids

Lead-bismuth eutectics (LBE) have considerable potential as a candidate material for accelerator-driven sub-critical systems(ADS).However,LBE corrosion and irradiation damage are two urgent challenges remaining to be solved for impellers of primary pumps.In this study,we have explored the possibility of using Fe-based amorphous coatings to overcome LBE corrosion and concurrently to sustain irradiation damage.Specifically,the Fe_(54)Cr_(18)Mo_(2)Zr_(8)B_(18)amorphous coating was prepared by high-velocity oxygen-fuel (HVOF) spraying on 316L steel and exposed to saturated oxygen static LBE for 500 h at 400℃.The coating with high thermal stability (T_(g)=615℃ and T_(x)=660℃) effectively prevented the substrate steel from being corroded by LBE owing to its unique long-range disordered atomic packing.The coating also exhibited strong irradiation resistance when being subjected to 45 dpa (displacement per atom) Au ion irradiation at room temperature,with no sign of crystallization even at the maximum implantation depth of 300 nm.Consequently,the hardness of the coatings before and after irradiation increased slightly.The current findings shed new insights into understanding corrosion mechanism and irradiation behavior of amorphous solids in LBE and expand the application range of amorphous materials.

Continuous chemical redistribution following amorphous-to-crystalline structural ordering in a Zr-Cu-Al bulk metallic glass

Bulk metallic glasses(BMGs)are thermodynamically metastable.As such,crystallization occurs when a BMG is thermally annealed at a temperature above the glass transition temperature.While extensive studies have been performed on the crystallization kinetics of BMGs,most of them have focused on the amorphous-to-crystalline structural ordering,and little attention has been paid to chemical distribution and its relationship with the structural ordering during the crystallization process.In this paper,a new approach,with simultaneous differential scanning calorimetry(DSC)and small angle neutron scatter-ing(SANS)measurements,was applied to study in situ the crystallization of a Zr_(45.5)Cu_(45.5)Al_(9)BMG upon isothermal annealing at a temperature in the supercooled liquid region.Quantitative analysis of the DSC and SANS data showed that the structural evolution during isothermal annealing could be classified into three stages:(Ⅰ)incubation;(Ⅱ)amorphous-to-crystalline structural ordering;(Ⅲ)continuous chemical redistribution.This finding was validated by composition analysis with atom probe tomography(APT),which further identified a transition region formed by expelling Al into the matrix.The transition re-gion,with a composition of(Cu,Al)_(50)Zr_(50),served as an intermediate step facilitating the formation of a thermodynamically stable crystalline phase with a composition of(Cu,Al)_(10)Zr_(7).

In Situ Scattering Studies of Crystallization Kinetics in a Phase-Separated Zr-Cu-Fe-Al Bulk Metallic Glass

Thermal stability and the crystallization kinetics of a phase-separated Zr-Cu-Fe-Al bulk metallic glass were investigated using in situ high-energy synchrotron X-ray and neutron diffraction,as well as small-angle synchrotron X-ray scattering.It was revealed that this glass with excellent glass-forming ability possesses a two-step crystallization behavior.The crystalline products and their evolution sequence are more complicated than a homogeneous Zr-Cu-Al glass with average glass-forming ability.The experimental results indicate that a finely distributed nanometer-sized cubic Zr_(2)Cu phase forms first and then transforms to a tetragonal Zr_(2)Cu phase,while the matrix transforms to an orthorhombic Zr_(3)Fe phase.The strength of the Zr-Cu-Fe-Al composite containing cubic Zr_(2)Cu phase and glass matrix increases,and the plasticity also improves compared to the as-cast Zr-Cu-Fe-Al bulk metallic glass.Our results suggest that the formation of multiple and complex crystalline products would be the characteristics of the Zr-Cu-Fe-Al glass with better glass-forming ability.Our study may shed light on the synthesis of bulk-sized glass-nanocrystals composites of high strength and good plasticity.

La_(2)Rh_(3+δ)Sb_(4):a new ternary superconducting rhodium-antimonide

Rhodium-containing compounds offer a fertile playground to explore novel materials with superconductivity(SC)and other fantastic electronic correlation effects.A new ternary rhodium-antimonide La_(2)Rh_(3)+δSb_(4)(δ≈1/8)has been synthesized by a Bi-flux method.It crystallizes in the orthorhombic La_(2)Rh_(3+δ)Sb_(4)-like structure,with the space group Pnma(No.62).The crystalline structure appears as stacking the two-dimensional RhSb_(4)-and RhSb_(5)-polyhedra networks along b axis,and the La atoms embed in the cavities of these networks.Band structure calculations confirm it as a multi-band metal with a van-Hove singularity like feature at the Fermi level,whose density of states are mainly of Rh-4d and Sb-5p characters.The calculations also imply that the redundant Rh acts as charge dopant.SC is observed in this material with onset transition at Ton c≈0.8 K.Ultra-low temperature magnetic susceptibility and specific heat measurements suggest that it is an s-wave type-II superconductor.Our work may also imply that the broad Ln_(2)Tm_(3+δ)Sb_(4)(Ln=rare earth,Tm=Rh,Ir)family may host new material bases where new superconductors,quantum magnetism and other electronic correlation effects could be found.